Isopropylbenzene (cumene) is widely used for making phenol, acetone and a-methylstyrene. Phenol is a feedstock in phenolic polymer manufacture and acetone is a by-product of the phenol production process. .alpha.-Methylstyrene is a feedstock for elastomeric polymers. Cumene is made by a direct alkylation reaction of propylene and benzene in the presence of an acidic catalyst. Cumene is then separated from reactants, by-products, contaminants and inert components in the reaction effluent by fractionation.
Heretofore, cumene manufacturing processes have generally employed an acidic catalyst such as solid phosphoric acid (SPA), aluminum chloride, and the like. Catalysts such as SPA can require the presence of water for activation and produce an extremely corrosive sludge by-product. The use of such sludge-forming catalysts involves special design considerations regarding corrosion, safety and disposal which are expensive to accommodate. Similarly, aluminum chloride catalyst requires anhydrous hydrochloric acid for activation. This corrosive catalyst system requires expensive corrosion-resistant materials in the construction of the reactor, and the spent catalyst also presents disposal problems. More recently, the introduction of new non-corrosive catalysts have reduced the need for the corrosion resistant alloys previously required.
U.S. Pat. No. 4,870,222 to Bakas et al. describes a process for the production of a monoalkylated aromatic compound which minimizes the production of undesirable alkylating agent oligomers, and produces monoalkylaromatics in high yields. The process entails the combination of an alkylation reaction zone, a separation zone and a transalkylation reaction zone wherein the alkylation catalyst and transalkylation catalyst are dissimilar and the catalysts comprise a silica-alumina material.
U.S. Pat. No. 5,198,595 to Lee et al. describes an acidic mordenite zeolite catalyst useful for producing a monoalkylated benzene product. The zeolite catalyst has a silica/alumina molar ratio of at least 40:1.
Other references in interest include U.S. Pat. Nos. 5,243,115, 5,055,627 and 5,176,883 to Smith, Jr. et al., 5,262,576 to Smith, Jr., 5,080,871 to Adams et al., 5,149,894 to Holtermann et al., 5,081,323 to Innes et al., 5,043,506 to Crossland, 4,950,834 to Arganbright et al., 4,347,393 to Miki, 3,855,077 to Bleser et al.; WO 91-18849; and WO 93-02027.